The present invention relates in general to a shaded pole motor having a stator assembly having two pole portions magnetically separated by a pair of pole-separation parts and, more particularly, to the stator assembly of the shaded pole motor.
A conventional shaded pole motor is disclosed in, for example, Japanese Patent Publication No. 59-39980, published Sept. 27, 1984. Such a shaded pole motor has a bore for rotatably receiving a squirrel-cage rotor. The bore is magnetically divided by pole separation grooves so that each divided portion has different magnetic poles with respect to adjacent portion and each of the poles has a shading coil to provide a delay in magnetic excitation so that the rotor is driven by a rotational magnetic field produced by the excitation delay caused by the shading coil.
The conventional shaded pole motor as described above has a rotational magnetic field effected by a pair of shading coils and, accordingly, the motor is substantially a so-called two-pole motor, which produces a large cogging, and consequently, large vibration and noise have been produced during low rotational speeds. Further, the maximum number of rotor rotations (N) is fixed at the condition of no-load as shown by: ##EQU1## wherein f is a frequency of a power source and p is the number of magnetic poles. In case of rotation with a load, the number of rotation will be less than the value of N (without a load) due to losses caused by slip, etc., of the rotor.